The existence of an outer ring in the Galaxy can explain the kinematics of OB associations in the Perseus and Sagittarius stellar-gas complexes. Moreover, it can also explain the orientation of the Carina arm with respect to the major axis of the bar. We show in this paper that the morphological and kinematical features of the sample of classical Cepheids are consistent with the presence of an R 1 R ′ 2 ring in the Galaxy.

This study analyzes the fractal properties of the space distribution of stars in the solar neighborhood, based on the Geneva-Copenhagen Survey data. We demonstrate the existence of dynamically weakly coupled stochastic fractal structures in the circumsolar stellar medium. The number of such structures in the real stellar medium on 3 to 20 pc scales significantly exceeds the number of similar structures in the corresponding simulated random distributions. The total number of fractal structures depends on their characteristic size – the scale factor ( Mf ). We demonstrate that the structuredness of the stellar medium increases with the scale factor reaching its maximum around Mf ~ 18 pc and has a minimum around Mf ~ 5 pc. For Mf = 5 pc, the number of fractal structures in the survey is equal to 688, while for Mf = 18−20 pc the corresponding number exceeds 4000, which differs by more than three standard deviations from the mean fractal dimension D for random distributions. Practically, no structures are observed in random distributions in this domain of fractal dimensions. The proportion of fractal structures with [Fe/H]> 0 increases slowly with increasing scale factor and the number of such structures remains in the interval from 170 to 900. On the whole, the number of structures with [Fe/H]< 0 varies with scale factor in the same way as the total number of structures, and lies in the interval from 530 ( Mf = 5 pc) to 3200 ( Mf = 20 pc). Such significant differences between the fractal properties of the real stellar medium and its random simulations are due to peculiar “gravitational viscosity” of the gravitating medium. The results reported may play an important part in the study of structural properties and dynamic processes in the Galaxy and in the investigation of relaxation processes in particular.

We analyze yet-unknown genetic links between open star clusters (OSCs) and galactic Cepheids and report the results of the new search for Cepheids – probable OSC members. A sample of 25% of the stars from a new catalog by Berdnikov (published in Melnik et al. 2015) which lists 674 Cepheids with reliable parameters was investigated. Based on photometric and kinematic data, we selected 17 Cepheids that are likely to be related to star clusters, four of which being new OSCs discovered by us.